The present invention relates generally to swept frequency acoustic interferometric (SFAI) determination of sound velocity and absorption in fluids and, more particularly, to the use of SFAI to noninvasively determine flow velocity and composition for flowing fluids.
Swept frequency acoustic interferometry (SFAI) [1] is an adaptation of the techniques of ultrasonic interferometry developed several decades ago for determining sound velocity and absorption in liquids and gases. In the original technique, and also in more recent modifications of the technique [2], the transducers (sensors) were placed in direct contact with the fluid being tested. This restricted the use of this technique to highly specialized laboratory characterization of fluids. By contrast, the SFAI technique extends the capabilities of the ultrasonic interferometry technique significantly and allows the noninvasive determination of velocity and attenuation of sound in a fluid (liquid, gas, mixtures, emulsions, etc.,) inside sealed containers (pipes, tanks, chemical reactors, etc.) over a wide frequency range. In addition, if the container material properties (density and sound velocity) are known, the liquid density can be determined using the SFAI technique. It has also been shown that it is possible to uniquely identify various chemical compounds and their most significant precursors based on the physical parameters of sound: velocity, attenuation, frequency dependence of sound attenuation, and density [3].
Oil companies have recently shown interest in noninvasive techniques for characterizing oil flow in pipes from oil fields.
U.S. Pat. No. 5,606,130 [4] states that it is anticipated that the SFAI measurements described therein can be performed on flowing samples in pipes. However, no mention is made therein of how to perform such measurements.
Accordingly, it is an object of the present invention to provide an apparatus and method for determining the composition of flowing fluids.
Another object of the invention is to provide an apparatus and method for determining the flow rate of a fluid.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the method for monitoring the composition of a fluid flowing through a vessel hereof includes the steps of: applying a continuous periodic acoustical signal to the outside of the vessel such that the acoustical signal is transferred to the flowing fluid, thereby generating vibrational resonance features having a plurality of maxima and minima therein; detecting the vibrational features generated in the flowing liquid; sweeping the continuous periodic acoustical signal through a chosen frequency range which includes two chosen consecutive maxima among the vibrational resonance features; and measuring the frequency difference between the two chosen consecutive maxima of the flowing fluid, whereby changes in the composition of the fluid are identified.
In another aspect of the present invention, in accordance with its objects and purposes, the method for monitoring the flow rate of a fluid through a vessel hereof includes the steps of: applying a continuous periodic acoustical signal to the outside of the vessel such that the acoustical signal is transferred to the flowing fluid, thereby generating vibrational resonance features having a plurality of maxima and minima therein; detecting the vibrational resonance features generated in the flowing liquid; sweeping the continuous periodic signal through a chosen frequency range which includes two chosen consecutive maxima in the standing-wave vibrational pattern; recording the frequency difference between the two chosen consecutive maxima to determine whether the composition of the fluid has changed; correcting the location of the resonance peaks in response thereto; and determining the frequency of one chosen resonance peak, whereby the flow rate of the fluid is determined.
In yet another aspect of the present invention, in accordance with its objects and purposes, the method for monitoring the composition of a fluid flowing at a flow rate through a vessel hereof includes the steps of: applying a continuous periodic acoustical signal to the outside of the vessel such that the acoustical signal is transferred to the flowing fluid, thereby generating vibrational resonance features having a plurality of maxima and minima therein; detecting the vibrational features generated in the flowing liquid; sweeping the continuous periodic acoustical signal through a chosen frequency range which includes one maximum among the vibrational resonance features; measuring the flow rate of the fluid; measuring the frequency of the maximum of the flowing fluid; and correcting the frequency of the maximum for the flow rate of the fluid, whereby changes in the composition of the fluid are identified.
In still another aspect of the present invention, in accordance with its objects and purposes, the method for monitoring the flow rate of a fluid having a composition and flowing through a vessel hereof includes the steps of: applying a continuous periodic acoustical signal to the outside of the vessel such that the acoustical signal is transferred to the flowing fluid, thereby generating vibrational resonance features having a plurality of maxima and minima therein; detecting the vibrational features generated in the flowing liquid; sweeping the continuous periodic acoustical signal through a chosen frequency range which includes one maximum among the vibrational resonance features; measuring the frequency of the maximum of the flowing fluid; determining the composition of the fluid; and correcting the frequency of the maximum for the composition of the fluid, whereby the flow rate of the fluid is determined.
Benefits and advantages of the present invention include the noninvasive measurement of flow rate and changes in composition of a flowing fluid.